It has long been assumed that chemical signaling is the language of life at sea, and the best way for microorganisms to interact (from symbiotic to parasitic relationships). However, the diffusion of chemical gradients is spatially limited. Are microorganisms also able to take long distance calls? Light, by its qualities (i.e., colors, intensity), and by its fluctuations (time, space), could be used for such a purpose. Most planktonic microorganisms are light-responsive (i.e., phototrophs, parasites), and can alter the local light seascape by scattering, absorption, and remission, or even by bioluminescence. Our proposed work will determine if microorganisms use light to communicate. To the best of our knowledge, our project will conduct the first experiments to assess the role of light communications in a controlled way (due to the use of novel light-emitting nanoparticles) within and between microbial species. If microorganisms use light in addition to chemical signaling, the consequence of our research will be analogous to the discovery of a new language. We expect that this paradigm shift will be important for: (a) ecologists and biologists, given that behavior is the cornerstone of resource acquisition; (b) microbiologists and modelers, considering the key role of inter-microbial interactions in controlling ocean biogeochemistry; and (c) applied sciences, as specific light signals may be harnessed to attract and concentrate specific microorganisms.